Aug. 3, 2012 -- Fitter kids do better on school tests, according to new research that echoes previous findings.

The fitter the middle school students were, the better they did on reading and math tests, says researcher Sudhish Srikanth, a University of North Texas student. He presented his research Friday at the American Psychological Association's annual meeting in Orlando.

The researchers tested 1,211 students from five Texas middle schools. They looked at each student's academic self-concept -- how confident they were in their abilities to do well -- and took into account the student's socioeconomic status.

They knew these two factors would play a role in how well the students did, Srikanth says.

After those factors, they looked at others that might influence school performance, such as social support, fitness, or body composition.

Bottom line? Of the other factors examined, "cardiorespiratory fitness has the strongest effect on academic achievement," he says.

The research doesn't prove cause and effect, and the researchers didn't try to explain the link. But other research suggests why fitness is so important, says researcher Trent Petrie, PhD, director of the Center for Sport
Psychology at the University of North Texas.

"Physical fitness is associated with improvements in memory, concentration, organization, and staying on task," he says.

Fitter Kids, Better Grades: Details

For one to five months before the students took standardized reading and math tests, they answered questions about:

Usual physical activity

Their view of their school ability

Self-esteem

Social support

The researchers assessed the students' fitness. They used a variety of tests that looked at muscular strength and endurance, flexibility, aerobic capacity, and body composition.

Previous studies have found a link between fitness and improved school performance, Srikanth says. However, this new study also looked at several other potential influences.

For the boys, having social support was also related to better reading scores.

For the girls, a larger body mass index was the only factor other than fitness that predicted better reading scores. The researchers are not sure why.

Other studies have found fitness more important than weight for test scores.

For both boys and girls, fitness levels were the only factors studied (besides socioeconomic status and self-concept) related to math scores.

Srikanth found an upward trend, with more fitness linked with better scores. He says he can't quantify it beyond that.

Fitter Kids, Better Grades: Perspectives

The new research echoes that of James Sallis, PhD, distinguished professor of family and preventive medicine at the University of California, San Diego. A long-time researcher on physical fitness, he reviewed the findings.

"The mountain of evidence just got higher that active and fit kids perform better in school," he says.

The finding that fitness was related to both reading and math scores in both girls and boys is impressive, he says. "That's strong evidence."

He is a co-founder of SPARK physical activity programs, in place nationwide.

Lesley Cottrell, PhD, vice chair of research in pediatrics at West Virginia University, has also linked fitness with better school performance in her research. "They extend our findings by considering students' self-concept," she says.

Her advice to parents? "A healthy child is a well-rounded child. Focusing on one developmental area may neglect other, important areas. For instance, in our findings we acknowledge that we have neglected the physical activity and fitness development for our children as a whole."

"By doing so, we may miss an opportunity to improve or sustain their academic development," she says.

The study was funded by the National Association for Sport and Physical Education.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

SOURCES: Sudhish Srikanth, University of North Texas student, Denton. James Sallis, PhD, distinguished professor of family and preventive medicine; chief, division of behavioral medicine, University of California, San Diego. Lesley Cottrell, PhD, vice chair of research, pediatrics, West Virginia University, Morgantown. American Psychological Association annual convention, Orlando, Aug. 2-5, 2012. Trent Petrie, PhD, professor of psychology and director of the Center for Sport Psychology, University of North Texas, Denton.